The present invention relates to a method for stabilizing antigenicity of a myeloperoxidase, and more particularly to a method for stabilizing antigenicity of an immobilized myeloperoxidase or a myeloperoxidase in solution.
A myeloperoxidase is an enzyme having hemes similar to heme a. The enzyme present in a leukocyte, mainly in a neutrophil, and carries out detoxication of bacterias and the like through halide ions.
In 1982, Davies et al. reported anti-neutrophil cytoplasmic antibodies. The antibodies were grouped into 2 subsets according to their stained pattern by indirect immunofluorescence technique (IIF). One subset is referred to as Cytoplasmic-ANCA (C-ANCA) and the other is referred to as Perinuclear-ANCA (P-ANCA). The myeloperoxidase is one of antigens for P-ANCA, thus it became to be utilized as an antigen having immunological functions.
In recent years, it has been noticed that quantification of an anti-neutrophil cytoplasmic antibody, such as P-ANCA, in a blood examination is useful for a diagnosis of renal diseases. Thus, a kit for enzyme immunoassay (EIA) including a myeloperoxidase as the antigen in the antigen-antibody reaction is commercially available. The enzyme immunoassay is carried out by the following procedure: First, the myeloperoxidase is allowed to adhere to an insoluble carrier such as a surface of synthetic resin plate by adsorption or the like, and to be dried. Next, a sample such as serum is applied to the above-mentioned carrier on which the myeloperoxidase is immobilized. A chromophore reagent or the like is added thereto, and then, the absorbance is measured.
However, since the antigenicity, namely the immunological property, of myeloperoxidase is unstable and easy to dissapear in any form, such as in a form of immobilized enzyme and in a form of aqueous solution, except in a form of freeze-dried powder, the myeloperoxidase cannot be stored for a long period such as more than 3 months. Therefore, once a solution of myeloperoxidase or an immobilized enzyme is prepared as a reagent, the reagent must be used thoroughly, otherwise the remaining reagent cannot be used later. The myeloperoxidase has a defect that a prepared reagent thereof is likely to be wasted.
An object of the invention is to provide a method for stabilizing antigenicity of a myeloperoxidase, particularly an immobilized myeloperoxidase or a solution of myeloperoxidase for a long period such as more than 6 months.
This and the other objects of the present invention will become apparent from the description hereinafter.